In Japan, digital satellite broadcasts have been performed corresponding to the standards of the ARIB (Association of Radio Industrial and Businesses). The standards of the ARIB are based on the DVB (Digital Video Broadcasting) standards used in Europe. The DVB standards uses the MPEG (Moving Picture Coding Experts Group) 2-TS (Transport Stream) system for broadcasting video and audio.
The MPEG2 system prescribes a system for multiplexing individual streams of encoded video, audio, and additional data and synchronously reproducing them. The MPEG2 system is categorized as two systems which are MPEG2-PS (Program Stream) and MPEG2-TS.
It has been supposed that the MPEG2-PS is used for transmitting and storing data in an error free environment. As a result, the MPEG2-PS allows the redundancy of data to be decreased. Thus, the MPEG2-PS has been used for digital stream media such as DVDs (Digital Versatile Discs), which use strong error correction codes.
In contrast, it has been supposed that the MPEG2-TS is used for transmitting and storing data in broadcasts and communication networks which are subject to errors. In the MPEG2-TS, since a plurality of programs can be contained in one stream, the MPEG2-TS has been used for digital satellite broadcasts and so forth.
In the MPEG2-TS, one transport stream is composed of a plurality of TS packets each of which has a fixed length of 188 bytes. The length of each TS packet of 188 bytes is decided in consideration of the integrity with the length of each ATM (Asynchronous Transfer Mode) cell.
One TS packet is composed of a packet header having a fixed length of four bytes, an adaptation field having a variable length, and a payload. In the packet header, a PID (Packet Identifier) and various flags are defined. The PID identifies the type of the TS packet.
A PES (Packetized Elementary Stream) packet containing discrete streams of video and audio is divided into a plurality of TS packets having the same PID number and the divided TS packets are transmitted. Video is encoded corresponding to for example the MPEG2 system. Audio of for example BS (Broadcast Satellite) digital is encoded corresponding to the MPEG2-AAC (MPEG2 Advanced Audio Coding) system.
As with packets for video and audio, a PES packet containing a subtitle or the like is divided into a plurality of TS packets and the divided TS packets are transmitted.
In addition, a transport stream contains packets of information described in tables of sections of PSI (Program Specific Information) and SI (Service Information). The PSI is information necessary for a system to select and receive a desired broadcast channel. The PSI contains a PAT (Program Association Table), a PMT (Program Map Table), an NIT (Network Information Table), a CAT (Condition Access Table), and so forth. The PAT describes a PID of the PMT corresponding to the program table and so forth. The PMT describes PIDs of video, audio, additional data, and a PCR (Program Clock Reference) contained in the corresponding program. The NIT describes the carrier frequency at which the objective program is being transmitted. The CAT describes the identification of the restricted receiving system and information with respect to discrete information such as contract information. The SI is a section used for services of the broadcast provider.
As satellite broadcasts based on the standards of the ARIB, digital CS (Communication Satellite) broadcasts and digital BS (Broadcast Satellite) broadcasts have been already started. In the digital BS broadcasts, besides conventional SDTV (Standard Definition Television) broadcasts, HDTV (High Definition Television) broadcasts have been performed. Digital satellite broadcast tuners which receive such digital satellite broadcasts have been developed.
Such a digital satellite broadcast tuner is provided with an IEEE (Institute of Electrical and Electronics Engineers) 1394 interface with which an AV (Audio Visual) system can be structured by combining a digital VCR (Video Cassette Recorder) and a personal computer. The IEEE 1394 provides an isochronous transfer and an asynchronous transfer. Using the isochronous transfer, video and audio data can be transferred at high speed. Using the asynchronous transfer, basic commands for mode control, program tuning, and so forth can be transferred.
When a transport stream received by such a digital satellite broadcast tuner is transferred to a digital VCR through for example an IEEE 1394 interface and recorded by the digital VCR, if all the received transport stream is transferred to the digital VCR and recorded thereby, TS packets which do not directly relate to the program are also recorded. As a result, the record capacity is unnecessarily wasted. In addition, a problem of the integrity of information takes place.
For example, as was described above, a transport stream contains a TS packet of the PSI and IS. In the PSI, the section of the NIT describes the frequency of the stream of the desired program in a plurality of streams of a plurality of carrier frequencies. In other words, the section of the NIT describes information about the overall network. Thus, although the information of the NIT is information of a plurality of streams of the overall network, information of one stream transmitted with one carrier is recorded by the VCR. Thus, when a TS packet of the section of the NIT is recorded by the VCR, the integrity of information cannot be kept.
The section of the EIT (Event Information Table) of the SI describes a program broadcast schedule. The information of the section of the EIT is used for an EPG (Electronic Program Guide) and timer recording. When a packet of the section of the EIT is directly recorded by the VCR, the integrity of the broadcast time of the EIT and the real time cannot be kept.
In such a manner, when a TS packet of information of the section such as the NIT describing the overall network and a TS packet of information of the section such as the EIT containing future time information are recorded, there is a possibility of which the integrity of information is not kept.
Thus, when a conventional digital satellite broadcast tuner outputs a stream through for example an IEEE 1394 interface, a partial transport stream is output.
From a partial transport stream, TS packets of the sections of such as the NIT and the EIT, which causes a problem about the integrity of information to arise, are removed. As a TS packet of the PSI, only information of the sections of the PAT and the PMT are output. As a TS packet of the SI, only information of the section of the SIT (Selection Information Table) composed of information of only a partial transport stream is output. In addition, when information is broken (for example, a channel is changed or the power is turned off), a packet of the section of the DIT (Discontinuity Information Table) is transmitted so that a problem about the integrity of information does not arise.
Details about a partial transport stream are described in “DVB ETS 300 468 Specification for Service Information (SI) in DVB systems,” ARIB-STD B1/B2 and ARIB TR-B15.
However, if a partial transport stream is output from the IEEE 1394 interface, information which is not permitted to be transmitted on a partial transport stream cannot be used.
For example, with the IEEE 1394 interface, a digital satellite broadcast tuner can be connected to not only a digital VCR, but various types of units such as a personal computer and a home server. For example, when a digital satellite broadcast tuner and a personal computer are connected with the IEEE 1394 interface, the received transport stream can be recorded to the HDD (Hard Disk Drive) of the personal computer and the pictures can be processed and edited.
In addition, if not only information of video and audio, but information of the sections of the PSI (Program Specification Information) and the SI (Service Information) can be transmitted from the digital satellite broadcast tuner to the personal computer, the information of the sections can be processed and used.
For example, the EIT (Event Information Table) describes information of a broadcast program schedule. The information of the broadcast program schedule is used for the EPG (Electronic Program Guide) and the timer recoding. If the information of the EIT can be transferred to the personal computer and used, a program schedule list can be created on the personal computer.
When a program schedule list has been created on the personal computer, information about programs, actors, and actresses can be easily searched on the Internet. In addition, on the personal computer, a user's original EPG screen which is different from an EPG screen displayed on the television can be created.
When information of the section of the EIT is transferred to the personal computer, the information can be used thereon and an original EPG can be created thereon.
However, as was described above, a stream which is output from a conventional digital satellite broadcast tuner through the IEEE 1394 interface is a partial transport stream. Information of the section of the EIT is not permitted to be transmitted on the partial transport stream.
Likewise, a transport stream which is broadcast contains a section of an SDT (Service Description Table) which describes information about a channel organization such as channel numbers, channel names, and a broadcast provider name. It can be supposed that the SDT is transmitted to a personal computer and the information thereof is used on the personal computer. However, the section of the SDT is not permitted to be transmitted on the partial transport stream.
Thus, an object of the present invention is to provide an information transmitting apparatus, a method thereof, an information processing apparatus, a method thereof, and an information processing system that allow information of a section which is not permitted to be transferred on a partial transport stream to be transferred to another unit when unnecessary TS packets are removed from a demodulated transport stream, information of a necessary section is inserted thereinto, and the resultant stream is output as a partial transport stream from an interface.